This application is in the field of mass spectrometers and, more specifically, to a mass analyzing spectrometer and method for fabricating a lens free collision cell. Various mass spectrometers are known in the art. An example of a prior art multi-pole mass spectrometer is illustrated in FIG. 1. For convenience of description, the mass spectrometer example of FIG. 1 is specific to a quadrupole mass analyzer, however embodiments of the invention may be used in other types of mass analyzers, e.g., a hexapole, an octapole, etc. In the mass spectrometer of FIG. 1, the sample molecules are delivered, e.g., by injector 105, into an ionization chamber 110, which ionizes the molecules, thereby acting as an ion source 110. Ions from the ion source 110 are focused and transferred to the mass analyzer 125 via ion guide or transfer optics 115, which is driven by voltage generator 120. The operation of a mass spectrometer is well understood by the skilled in the art.
An ion collision cell is incorporated in various designs of mass spectrometers, such as the triple quadrupole mass spectrometer instrument described in FIG. 3. The function of a collision cell is to modify the ions generated in the ion source, by either colliding them into fragments or to react them with other molecules. In both cases, a parent ion from the ion source is introduced into a higher-pressure region for a given time. A specifically selected gas, such as argon, nitrogen, helium, etc, is injected into the high pressure region of the collision cell, so that the ions will collide with molecules of the injected gas. The resulting fragment or product daughter ions then exit the collision cell and are analyzed by another mass analyzer and further directed to the detector.
The collision or reaction energy can be varied by the parent ion's initial velocity, the size and type of the collision gas molecules, and the number of collisions encountered. The number of collisions is depended on the gas pressure and the reaction time. If a parent ion hits a collision gas molecule, its flight path will be altered. For this reason most cell designs are built around multi-pole structures containing an ion focusing RF field.
The high pressure inside the collision cell needs to be accurately controlled, while the remaining interior of the mass spectrometer needs to be maintained in vacuum. However, gas may leak from the collision cell into the mass spectrometer through the openings for ions entering and exiting the cell. Prior art collision cells utilize seals at the entrance and exit to the cell to reduce the gas leak. However, such seals may be insufficient for high performance cell. Further information can be found in U.S. Pat. No. 6,576,897.
Accordingly, there is still a need for an improved and effective collision cell.